1. Field of the Invention
This invention relates to a storage vessel which maintains a clean environment and stores such articles as those to be free from contamination. More particularly, this invention relates to a storage vessel which stores such articles as semiconductor wafers, compact discs, etc.
2. Prior Art
A prior art storage vessel is shown in FIG. 2. In FIG. 2, the vessel has a storage vessel case 41 housing a shaft 42 which is rotatably supported by a bearing 45 fixed to the case 41 via a support. A plurality of carrier receivers 43 are circumferentially disposed on shaft 42, on which stock shelves or carriers 47 are located spaced a certain distance from the shaft.
An AC servomotor 46 fixed to the case 41 via the support drives the shaft 42 and consequently the plurality of carrier receivers 43 will rotate in a generally horizontal plane. An air supply duct 48 provided on the upper part of the storage vessel case is furnished with a filter 49, and air introduced through the air supply duct 48 as shown by broken lines and arrows A is filtered by the filter 49 and lead into the storage vessel case. In addition, an air circulating blower 50 is equipped at the lower part of the storage vessel case 41, and air blown by the blower 50 is filtered by a filter 51 and circulated in the storage vessel case 41 as shown by broken lines and arrows B.
In case articles such as wafers should be stored for a long period of time, the storage vessel may be provided with a nitrogen sealing system and/or a temperature control system, or the like, to prevent the article surfaces from being oxidized.
The bearing 45 used in the above-mentioned storage vessel is of a contacting type, which caused problems by generating oil mist or dust thus contaminating stored articles being kept for a long period of time.